Aircraft such as the ones commonly utilized in military applications are known to employ multiple stage geared rotary actuators. Such actuators are provided for positioning the leading edge flaps and/or the trailing edge flaps, but such actuators have an inherent failure mode that could fatigue the flight control panel of the aircraft if the inherent failure mode goes undetected. Moreover, if undetected, the fatigue resulting from failure in the multiple stage geared rotary actuators could ultimately result in loss of the flight control panel.
Conventionally, the geared rotary actuators are constructed to have multiple output stages each with a planetary gear set. Each planetary gear set includes a fixed ring gear and a ring gear connected to the flight control panel, and a failure is difficult to detect because the remaining output stages that can drive the flight control panel will back-drive an output stage through the panel being controlled. As a result, loading is introduced within the flight control panel which it is not designed to carry.
As will be appreciated, flight control panels have both aiding and opposing loads imposed upon them dependent upon the position of the panels. It is recognized as a good design practice to protect both the actuator system and the flight control panels, e.g., leading edge flaps, in the unlikely event of a torque tube failure which could eliminate the resisting or holding torque from a power drive unit that would normally resist aiding loads imposed upon the panel. For this purpose, various methods can be incorporated for such a failure, i.e., asymmetry brakes, zero back-driving actuators, dual load path shafting, etc.
Presently, it is an acceptable method to utilize dual load path shafting to multiple actuators per panel. Should a shaft or the internal construction of a geared rotary actuator fail open, then the flap panel must be held. Generally, the flap panel is held by the other load path to another actuator reacting to aiding loads on that flap panel.
In some military applications, aircraft design dictates that only one geared rotary actuator drive a single flap panel. Alternatively, multiple actuators are utilized in which only one actuator is sized to react to aiding loads on a flap panel. When a system is configured in this fashion, it is necessary to have dual load path shafting and also to incorporate fail safe construction for the actuator system.
The present invention is directed to overcoming the above stated problems and accomplishing the stated objects by providing an actuator system for control panels of an aircraft.